MRI brain protocol and sequence
MRI brain in the latest and advanced computer-based cross-sectional imaging modality provides both anatomical and physiological information of the brain. It is non-invasive, which means no radiation is involved. The brain is the most frequently imaged organ by Magnetic resonance imaging.
Indications for MRI brain
- Headache
- Trauma
- Seizure
- Multiple sclerosis
- Infraction
- Hemorrhage
- Hearing loss
- Visual distance
- Unexplained neurological symptoms deficit
- Mapping of brain function
Patient preparation
Before preparation:
Take a complete history from the patient, if in case the indications are not clear referring physician should be contacted.
All the metallic and artifact-causing objects needed to remove.
Disposable earplugs should be provided to each patient to devoid the patient from repeated noise during scanning.
It is important to instruct the patient to avoid coughing or producing other large voluntary movements during or in between the scans.
Ensure the IV line prior to the pre-contrast acquisition preferably with IV cannula 20 or 22 gauzes.
Contrast media
Gadolinium-based contrast media is given to enhance is useful in brain imaging. It is often believed that the contrast media (gadolinium) is indicated for all the lesions.
IV- Gadolinium: 0.1-0.2 mmol/kg of body weight
-is given as a bolus at the rate of 1ml/sec.
-like a slow infusion at a rate of 1ml/sec.
Prepare the head coil.
Patient position:
The patient lies in the supine position with the head first.
Topogram positioning / Landmark- Center the FOV on the glabella in the midline.
MRI Brain Protocols
Routine brain Protocol
Sequence-
– Scout: 3 plane localizers
– T2 FSE in the axial plane
– T2 FLAIR in the axial plane
– T1 SE in the sagittal plane & coronal plane
– DW EPI based in the axial plane
– Post-contrast – T1 SE in the axial plane and coronal plane
Axial sequence
- The plot on the sagittal plane
- Parallel to the line joining the genu and splenium of the corpus callosum
- FOV- 220-240mm
- Slice thickness- 5-6mm
- Saturation slab- parallel to the slices, inferior to the most caudal slice and thickness of approx. 50-80mm
- Matrix- 512 x 512
T1 weighed
- Repetition time, TR- 364ms
- Echo time, TE- 15ms
T2 weighed
- Repetition time, TR- 4500ms
- Echo time, TE- 100ms
Signal intensities seen | CSF | FAT | White matter | Grey matter | Bleed | Gadolinium |
T1 | DARK | BRIGHT | BRIGHT | DARK | BRIGHT | BRIGHT |
T2 | BRIGHT | DARK | DARK | BRIGHT | BRIGHT | DARK |
FLAIR
- TR- 10717ms
- TE- 100ms
- T1- 2000ms
- Pathology appears hyperintense due to the optimization of the T1 sequence required to null the signal of water.
Advantages of FLAIR:
- Cerebrospinal fluid (CSF) appears low intensity or FLAIR which has two advantages:
- The periventricular lesion is superiorly differentiated from CSF.
- Infections exudates may replace cerebrospinal fluid (CSF) in the sulei to appear hyperintense on the images of the FLAIR sequence.
Sagittal Sequence
- Plot on the coronal or axial localizer
- Same slice thickness, saturation slab, and gap.
- Sagittal images are essential in the evaluation of the sellar, Parasellar lesion, posterior fossa lesion, and intraventricular lesion and also for evaluation of vascular anatomy.
Coronal sequence
- Plot on the sagittal plane localizer
- Parallel to the posterior surface of the brain stem.
Diffusion-Weighted sequence
- Necessary for all the patients of stroke
- DWI in brain tumor- to detect and characterize the chemotherapy response in tumor and also accessing the chemotherapy response in the tumor.